The policeman who was injured in the nerve angent attack on a former Russian spy is now talking according to the home secretary, Amber Rudd.

Counter terrorism officers are working to trace the origin of the nerve agent used in the attempted murder of ex-Russian spy Sergei Skripal and his daughter, Yulia, in Salisbury on Sunday.

Both remain in a critical condition after they were found on a bench in the city.

But a police officer, who was in intensive care, is now "engaging and talking with people", but remains in a serious condition.

The home secretary revealed the news on the officer while also defending the government's response to the situation which has been criticised by Moscow.

At the start of the week, the foreign secretary Boris Johnson suggested that part of the England football team delegation may not travel to the world cup this summer which takes place in Russia.

Speaking to Radio 4, Rudd said: ""Let me be clear, we are absolutely robust about any crimes committed on these streets of the UK."

It was confirmed on Wednesday that a nerve agent was used in the attack, though officials are remaining tight-lipped on further information.

Assistant Commissioner Mark Rowley said: "Having established that a nerve agent is the cause of the symptoms... I can also confirm that we believe that the two people who became unwell were targeted specifically."

Russia have been highly critical of the UK's reaction to the attacks and have accused officials of being involved in a targeted campaign against the Kremlin.

Parallels have been drawn up with the death of former agent Alexander Litvinenko.

In 2006, Alexander Litvinenko, the Russian dissident and former intelligence officer died in London after he drank tea laced with a radioactive substance polonium.

Police are still appealing for any more information from witnesses at the scene.

Particularly those who were in the centre of Salisbury on Sunday afternoon (3 March) or those who who ate at Zizzi or drank in the Bishop's Mill pub between 1pm and 4pm.

Both sites remained closed off the the public.